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Yeah she's still worth training.
She can be the movement unit( she can reposition and have allies cover more ground with her prf weapon), Or give her bladetome,with +spd and potentially Flyer buffs she won't struggle killing for the most part ( any unit that is'nt blue and has high res will most likely die from two of her shots)

Absolutely, especially if you go the blade tome route. Speed is incredibly potent on a blade mage, and attack is less of a problem when you are getting +24 attack from hone/fort emblem buffs. I have a +Spd/-Atk green Olwen who has base 26 attack and she still just murders everything due to how potent horse emblem buffs are.

Otherwise, her PRF tome is an incredible mobility asset that can really turn the tides of battle. She's a very solid unit with some decent build options.